Special Functions
Special Functions
Launch Control (racing start function)
This function is available both in selector lever positions "D" and "M" in Sport Plus mode. Preconditions are as follows: Vehicle stationary, brake applied, kickdown active. The function is triggered by releasing the brake. The double clutch in the transmission now allows optimum wheel slip for maximum acceleration. Stress on components increases significantly when driving off at maximum acceleration compared with driving off "normally". In addition, the components in the clutches are exposed to high levels of thermal stress. Therefore, the clutches are cooled with the maximum cooling volume flow to protect the components.
Prevention of downshifts in deceleration state, e.g. when approaching a corner (Fast Off)
If the driver decelerates, i.e. releases the accelerator pedal quickly, when approaching a corner, the currently engaged gear is retained. If the driver also applies the brakes now, downshifts adapted to the vehicle speed are performed so that engine braking torque is available when approaching a bend and the vehicle can be accelerated out of the bend in the optimum gear. If the accelerator pedal is now moved towards throttle valve "open" again, gear changes are performed once again according to the driver's requests. This function responds differently, depending on which mode was selected. If "Normal" mode is selected, the function is only activated for a high negative accelerator pedal gradient. In "Sport" mode, the function is activated for a medium negative accelerator pedal gradient, while it is activated for a low negative accelerator pedal gradient in "Sport Plus" mode.
Downshifts while braking (Fast Back)
A downshift is initiated immediately if the driver switches quickly (within approx. 1 second) from accelerating to braking. However, the sportiness characteristic and the selected mode dictate how early a downshift is initiated.
Gear retention while cornering
Lateral acceleration is detected via the lateral-acceleration sensor (single component with yaw rate sensor), which is located under the center console and works for the PSM system, and the engaged gear is retained, depending on the shift map, engaged gear and lateral acceleration.
Active switching to a sporty map
For increased spontaneity, the system switches to a sporty and dynamic map when the driver uses fast, positive accelerator pedal movements. The previous map is then activated again afterwards. This function is intended, for example, for situations in which a driver is driving at an extremely comfortable speed on a country road, but now decides to overtake and wants the vehicle to drive dynamically for a short time.
Manual momentary intervention in selector lever position "D"
To enable manual downshifts even in the automatic gear-selection gate, for example:
- when approaching a corner
- when entering speed zones/small towns
- when driving downhill
the upshift and downshift buttons (both on the steering wheel and on the selector lever) are active in the automatic gear-selection gate. In other words: PDK transmission switches to the manual program when the corresponding button is pressed. "M" appears in the instrument cluster and the requested gearshift is performed. At the same time, an 8-second timer is started in the control unit. If the upshift or downshift button is pressed again within this 8 seconds, the timer is restarted.
The PDK transmission automatically switches back to Automatic mode ("D" appears in the instrument cluster) if:
- the timer runs out, no cornering is performed and the vehicle is not in deceleration state
- the selector lever is moved from "D" to "M" and back to "D"
Automatic upshifts and downshifts at the engine speed limits remain active. The deceleration downshift function is also active.
Warm-up Program
The warm-up map is a shift program with raised gear-changing points, which has the effect of heating the catalytic converters to their operating temperature as quickly as possible. The engine and transmission also reach their operating temperature more quickly with this map. The coolant temperature of the engine is checked when the engine is started. If the temperature is less than approx. 68 °F. (20 °C.), the warm-up programme is activated and is deactivated again when the coolant temperature reaches 86 °F. (30 °C.).
Overheating Protection
Various measures are implemented on the transmission in order to protect the transmission and double clutch from overheating. The temperature sensor, which is installed above the hydraulic control unit and measures the oil sump temperature, is used for this purpose. A calculation model which calculates the clutch temperature from the engine torque and the slip at the clutch, is also used. Overheating protection is activated in several stages and actively prompts the driver to adapt his driving style in advance.
If the temperature continues to rise (oil sump temperature
more than 293 °F./145 °C.), stage two is activated. This means that jerking continues. The engine torque and kickdown revs are reduced more drastically in this case. The white warning "Transmission temperature too high" appears in the instrument cluster. Another fault is stored in the fault memory.
If the temperature rises even further (oil sump temperature
more than 302 °F./150 °C.), emergency run "Transmission emergency run" appears in the instrument cluster. Shortly afterwards, the double clutch is opened completely and power transmission is no longer available. Another fault is stored in the fault memory. If the driver now presses the accelerator, the vehicle will drive off, but not with the usual level of comfort. After implementing these measures, the transmission activates a special shift program in which gear changes are performed very slowly and uncomfortably. Once the temperature falls below a certain temperature threshold, the transmission reverts to its normal program.
Clearly perceptible jerking occurs in the first stage (at an oil sump temperature more than 275 °F./135 °C.) due to continuous opening and closing at drive-off or crawling speed, thereby prompting the driver to change the driving situation. Engine torque and kickdown revs are also reduced and a fault is stored in the control unit.
Upshift suppression for 7th gear
7th gear is designed as an overdrive on the Porsche Doppelkupplung (PDK). This means that in various driving situations (high road resistance, for example), the vehicle would decelerate when 7th gear was engaged. As a result, 7th gear is not engaged in such situations.
Upshift interruption
In automatic transmissions, the time that elapses between triggering a change in speed and starting to change speed is called the response time. Naturally, this response time depends on the shift program and the shifting characteristic curve.During this time, the driver does not yet notice that the gear change has already started. If the driver's intention changes (the driver quickly removes his foot from the accelerator, for example), the upshift that has started is interrupted provided the engine speed remains unchanged.
One-touch hold function
The one-touch button on the steering wheel or the selector lever must be held in a downshift ("-") or upshift ("+") direction in order to engage the lowest or highest possible gear in the manual gate. Tipping the button back initially triggers the first gear change in accordance with the touch command. The next-lowest or next-highest gear is then always engaged by holding the button. This saves the driver from having to touch the button repeatedly. This function is switched off after 25 seconds to prevent malfunctions.
Stationary decoupling
When the vehicle comes to a stop, the clutch is generally. opened as long as the brakes are applied. However, the clutch remains slightly engaged in order to take full advantage of crawling. The reason for this measure is reduced fuel consumption.
Drive-Off Assistant
If the vehicle is stopped on an incline, the driver will apply the brake and set a certain brake pressure. When the driver now switches from the brake pedal to the accelerator pedal in order to drive off, the set brake pressure is maintained for as long as it takes for the vehicle to drive off. This prevents the vehicle from rolling back while the driver is switching pedals.
Tow-starting/towing
Never lift the vehicle at just one axle when towing all-wheel-drive vehicles. The vehicle cannot be tow-started, nor should this be attempted due to the risk of serious damage to the transmission.
When the engine is not running, adequate lubrication of the transmission is not guaranteed. Therefore the following points must be observed:
1. Engage selector-lever position "N"
2. Top speed = 30 mph (50 km/h)
3. Maximum towing distance = 30 miles (50 km)
4. In the case of long towing distances, the all-wheel-drive vehicle must be transported on a trailer.
Driving off in manual or with accelerator pedal position more than 60%
Procedure when driving off:
1. Driver presses the accelerator pedal, acceleration begins, clutch 1 enters the slip phase, vehicle moves off
2. Slip phase ends for clutch 1, further acceleration is accomplished with closed clutch
3. Clutch 1 opens while clutch 2 closes, short transition phase
4. Gear change has been completed, further acceleration is accomplished in 2nd gear
Driving off with accelerator pedal position approx. 10% to 60%
The implementation of comfort mode when driving off represents an innovative development. With this feature, the large drive-off torque of 1st gear is used to build up acceleration at low to average partial loads, depending on the driver request and driving program. The subsequent upshift into 2nd gear is performed seamlessly by means of an intelligent clutch slip management system in the two clutches. The result is an impressive drive-off performance that is both extremely comfortable and smooth.
Procedure when driving off:
1. Driver presses the accelerator pedal, both 1st and 2nd gear are engaged, both clutches enter the slip phase
2. Engine speed is constant, clutch 2 begins to close
3. Clutch 2 closes, engine speed remains constant
4. Clutch 2 is closed, further acceleration in 2nd gear without any increase in engine speed